It is to be noted that under the term “network environment” in the sense as used in connection with the description of the present invention there is to be understood for example a communication network system, a network environment for an organization, a network environment for a plant, or the like.
However, for descriptive purposes which are by no means intended to be limiting the present invention, a communication network system has been chosen as an example for illustrating the present invention.
In connection with the thus chosen example, the expression “data element” is associated to a subscriber to said communication network, i.e. data element information mean subscriber related information. Nevertheless, this is not limiting and in other network environments, data elements may be associated suitable other information such as employee information in a network environment for an organization, or product information in a network environment for a plant.
In connection with the thus chosen example, the expression “request routing” is associated to a signaling within said communication network. Nevertheless, this is not limiting and in other network environments, to the term request routing may be associated a suitable other meaning than signaling.
In the recent years, communication networks have become more and more popular and accepted by a continuously increasing number of communication network subscribers. In order that such communication networks function properly, subscriber data have to be kept in the network and made available to network entities involved in establishing communication to and/or from a respective subscriber and his communication partner. Conventionally, such subscriber data are maintained in a so-called home location register HLR in case a GSM network is concerned (GSM=Global Standard of Mobile Communication).
With the progress in communication networks and the development of the so-called third generation (3G) networks also referred to as UMTS network (Universal Mobile Telecommunication System) the functionality previously implemented into the home location register HLR has been transferred to a so-called home subscriber server HSS functional entity. The home subscriber server HSS is the master database for a given user (subscriber). It is the entity containing the subscription related information to support the network entities actually handling calls/sessions in which the user is involved.
For example, the home subscriber server HSS could provide support to the call control servers in order to complete the routing/roaming procedures by solving authentication, authorization, naming/addressing resolution, location dependencies and so on.
In particular, the home subscriber server HSS is responsible for holding the following user related information:                user identification, numbering and addressing information        user security information: network access control information for authentication and authorization        user location information at intersystem level; HSS handles the user registration and stores inter-system location information and so on        the user profile (services, service specific information . . . )        
Based on the information held in the home subscriber server, the home subscriber is also responsible for supporting call control (CC) and/or subscriber management (SM) entities of different control systems (circuit switched domain control, packet switched domain control, IP multimedia control) offered by the operator.
The above mentioned third generation communication networks rely on the Internet Protocol (IP). Nevertheless, the present invention as to be described hereinafter is not limited to third generation communication networks and/or on communication networks making use of the Internet Protocol.
Rather, the third generation network operated on the basis of the Internet Protocol is chosen as an illustrative example only. In particular, the present invention is applicable to all communication networks in which subscriber related information is kept in a plurality of subscriber information database entities.
With the increase in the number of subscribers to a network and also with the increase of the networks and network complexity, the likelihood of a failure of either a network entity and/or an interface between network entities is likely to increase. In order to assure a continuous operation for a communication network even in case of a failure situation occurring somewhere within the network, the subscriber data have to be held available all the time.
Previously, providing a copy of the subscriber database was one approach. Such a copy (also known as back-up) of the database was established for example after regular intervals. However, during the time required for backing-up it is at least difficult to provide the full performance of the communication network. Still further, new subscriber data and/or changed subscriber data are not kept track-off unless a backup of the subscriber database entity is performed. Thus, if a database entity brakes down after the recent backup and before a subsequent backup, new and/or amended data contained in the database entity are difficult to be restored on the basis of only the backup database.